Aquatic?

[Arryn]

deccan said:
Yeah but landsters find it hard to take sea provinces because all they can build in it are crappy tritons and they can't build forts underwater. So just taking one sea province isn't all that useful.

The L7 Conjuration spell Living Castle (N4W1) creates an underwater fortress. I point this out to you because landlubbers *can* create underwater forts. It just requires powerful, expensive magic.